chore: add AGENTS.md file

[amanabiy]

Issue #, if available:

Description of changes:
Adds AGENTS.md file, a guide

related: X2NaAdxtpFej 0w2zAaLmmgWn

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.90%. Comparing base (b6d9bd6) to head (9ab365d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #210   +/-   ##
=======================================
  Coverage   98.90%   98.90%           
=======================================
  Files          44       44           
  Lines        1185     1185           
  Branches      318      318           
=======================================
  Hits         1172     1172           
- Misses         12       13    +1     
+ Partials        1        0    -1     

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